DO TRANSMURAL LEFT VENTRICULAR BIOPSIES FROM ASYNERGIC SEGMENTS PROVIDE ACCURATE REPRESENTATION OF TISSUE VIABILITY? Transmural left ventricular (LV) biopsies are obtained during coronary artery bypass surgery to determine the histomorphologic characteristics of viable and non-viable myocardium. In this study, we determined the extent of variation in the collagen content of adjacent, small (biopsy-equivalent) transmural sections of asynergic LV myocardium. In 13 explanted hearts of men with chronic ischemic heart disease, volume fraction of collagen was measured in 2 large mid-LV anterior wall segments per patient. Each of the 26 segments (surface area 3+1cm2, thickness 10.4+3.7mm)were stained histologically with picrosirius red and volume fraction of collagen was measured by computerized videodensitometry in the entire specimen. The 26 large segments were then divided into 261 small, 2mm-wide (biopsy-equivalent), consecutive transmural sections and volume fraction of collagen was measured in each section. In addition, relation between pre-transplantation quantitative thallium uptake and post-transplantation percent collagen content was assessed in the 26 large segments and 261 small sections. Of the 261 sections, 122 (47%) had volume fraction of collagen outside the 95% confidence interval of the 26 larger segments. Compared with the 26 segments, the 2mm-wide sections overestimated or underestimated the myocardial collagen content by >20% in 28 (11%) sections, by >10% in 83 (32%) sections, and by >5% in 137(52%) sections. The findings persisted when the data were analyzed using the individual heart (patient) as the unit of analysis. Moreover, the difference in the collagen content of adjacent 2mm-wide sections was independent of the presence or absence of viability by histomorphology or by thallium SPECT. The significant variation in volume fraction of collagen observed within adjacent 2mm-wide, biopsy-equivalent, transmural LV sections attests to the rather continuous nature of structural damage in coronary artery disease. Thus, designation of asynergic segments as viable or non-viable on the basis of transmural LV biopsies should take into consideration this wide variation in collagen content of small LV samples.